Although most people prefer the winter months, June is a good time to visit Yercaud. Infact, October to June is the preferred time, since monsoon starts from July. Weather would be pleasant for the most part, although bright and humid. You can enjoy the drive. Two Days would be sufficient to cover Yercaud if you start your day early. If you've 3 Days, you can cover all the places leisurely. Some places to See: Servarayan Temple, Lake, Boathouse, Deer/Peacock park, Arthur's Seat, Pagoda Point, Ladies Seat point, Children's Seat Point, Kiliyur falls, ATV quad biking at Grange resorts, Karidiyur View Point, Tipperary View Point, Anna Park, Sri Raja Rajeswari Temple, Heaven's Ledge
Map: http://4.bp.blogspot.com/-huCbDwAjiz8/UePeFD5lQ9I/AAAAAAAADUw/-_cj7Z3W6cI/s1600/tourist-map-y.jpg Food: Very few options are there. Best to have food at the Resort you are staying or head over to "Sri Saravana Bhavan Elite" near lake circle, Manjakuttai Rd.